真题
1 . 如图所示,过
外一点
作一条直线与
交于
,
两点,已知
,点
到
的切线长
,则弦
的长为_______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b80ee363635d73f601654339028daec.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f5fca8c94add435f4aefb933ffe55a01.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
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真题
2 . 选修4-1:几何证明选讲
如图AB是
直径,AC是
切线,BC交
与点E.
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/4728723fed18470d84dbc7e44107ef4f.png)
(Ⅰ)若D为AC中点,求证:DE是
切线;
(Ⅱ)若
,求
的大小.
如图AB是
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/f611407c50d540ad9104c02c63aee4ba.png)
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/f611407c50d540ad9104c02c63aee4ba.png)
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/f611407c50d540ad9104c02c63aee4ba.png)
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/4728723fed18470d84dbc7e44107ef4f.png)
(Ⅰ)若D为AC中点,求证:DE是
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/f611407c50d540ad9104c02c63aee4ba.png)
(Ⅱ)若
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/67dc69fe27884a1a8ff1aaa71bdd61c7.png)
![](https://img.xkw.com/dksih/QBM/2015/6/24/1572143053012992/1572143059132416/STEM/ce093531127143b1baddcccf84486568.png)
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